1. Field of the Invention
The present invention relates to a method for manufacturing a magneto-resistance effect element which is configured such that a current is flowed in the direction perpendicular to the film surface thereof to detect the magnetization of the element and the magneto-resistance effect element.
2. Description of the Related Art
Recently, the performance of a magnetic device, particularly such as a magnetic head is enhanced by means of Giant Magneto-Resistive Effect (GMR). Particularly, since a spin valve film (SV film) can exhibit a larger GMR effect, the SV film has developed the magnetic device such as a magnetic head and MRAM (Magnetic Random Access Memory).
The “spin valve” film has such a structure as sandwiching a non-magnetic metal spacer layer between two ferromagnetic layers and is configured such that the magnetization of one ferromagnetic layer (often called as a “pinning layer” or “fixed magnetization layer) is fixed by the magnetization of an anti-ferromagnetic layer and the magnetization of the other ferromagnetic layer (often called as a “free layer” or “free magnetization layer”) is rotated in accordance with an external magnetic field.
The spin valve film is employed for a CIP (Current I plane)-GMR element, a CPP (Current Perpendicular to Plane)-GMR element and a TMR (Tunneling Magneto Resistance) element. In the CIP-GMR element, a sense current is flowed to the SV film in the direction parallel to the film surface thereof. In the CPP-GMR element and the TMR element, a sense current is flowed to the SV film in the direction almost perpendicular to the film surface thereof. In view of the development of a high density recording head, attention is paid to such an element as configured so that the sense current is flowed perpendicular to the film surface.
In a metallic CPP-GMR element, since the SV film is composed of metallic films, the resistance change by the magnetization change of the free layer becomes small so that weak magnetic (from a magnetic disk of high recording density) field can not be detected.
In contrast, such a CPP element as containing an oxide layer with current path therein (NOL: Nano-oxide layer) is proposed (Reference 1). In the CPP element, the element resistance and the MR variation degree of the element can be developed by means of CCP (Current-confined-path) element. Hereinafter, the CPP element is often called as a “CCP-CPP element”.
[Reference 1] JP-A 2002-208744 (KOKAI)
Such a magnetic recording device as an HDD is widely available for a personal computer, a portable music player and the like. In the future, however, the reliability of the magnetic recording device is severely required when the usage of the magnetic recording device is increased and the high density recording is also developed. It is required, for example, that the reliability of the magnetic recording device is developed under a high temperature condition or a high speed operation. In this point of view, it is desired to much develop the reliability of the magnetic head in comparison with the conventional one.
Particularly, since the CCP-CPP element has a smaller resistance than the one of the conventional TMR element, the CCP-CPP element can be applied for a high end magnetic recording device of server enterprise requiring higher transfer rate. In the use of the high end magnetic recording device, both of the high density recording and the high reliability must be satisfied. Also, the high reliability under a higher temperature condition must be preferably satisfied. In other words, the CCP-CPP element is required to be used under the more severe condition (e.g., high temperature condition) and the more severe operation (e.g., the information being read out while the magnetic disk is rotated at high speed).
Since the resistance of the CCP-CPP element is small, the CCP-CPP element can exhibit some advantages such as high frequency response and high density recording correspondency. Since the three-dimensional structure of the NOL is very complicated, the NOL structure can not be almost realized as designed. In contrast, in order to realize the server enterprise requiring severe specifications, the NOL structure must be formed as designed.